Compatibility of Trichoderma isolates with pesticides used in lettuce crop

ABSTRACT Lettuce drop, caused by Sclerotinia minor and S. sclerotiorum, is one of the most important diseases that affect lettuce crop in Brazil. In previous studies, isolates of Trichoderma asperellum (IBLF 897, IBLF 904 and IBLF 914) and T. asperelloides (IBLF 908) were selected for the biocontrol of this disease. In this subsequent study, the compatibility of these isolates with pesticides used in lettuce crop in Brazil was evaluated. Initially, the mycelial growth of isolates was evaluated in culture medium plus pesticides. Then, the effect of pesticides on the parasitism of T. asperelloides isolate IBLF 914 in baits and sclerotia of S. minor and S. sclerotiorum, as well as on the survival of lettuce seedlings, was evaluated in gerboxes after application on baits and sclerotia of the antagonist with pesticides at their respective commercial doses. The fungicides pencycuron and mandipropamid and the insecticide imidacloprid did not affect the mycelial growth of Trichoderma isolates. The fungicide iprodione did not affect the mycelial growth of T. asperellum isolates. but the isolate of T. asperelloides was sensitive from the concentration of 10 µg.L-1 fungicide. Procymidone reduced the mycelial growth of Trichoderma isolates from the concentration of 10 µg.L-1 fungicide, and azoxystrobin reduced the conidial germination of the isolates of the antagonist, showing LD50 between 0.36 and 0.42 µg.L-1 fungicide. On the other hand, in the experiment carried out in “gerboxes”, none of the pesticides reduced the parasitism of baits and sclerotia or reduced the control of S. minor and S. sclerotiorum in lettuce seedlings. Results indicate that the biological control of lettuce drop with T. asperelum isolate IBLF 914 can be compatible with the remaining phytosanitary treatments used in lettuce crop.

摘要：由小核盘菌（Sclerotinia minor）和核盘菌（Sclerotinia sclerotiorum）引发的生菜菌核病，是巴西生菜种植中最具危害性的病害之一。既往研究中，研究者筛选出棘孢木霉（Trichoderma asperellum）菌株IBLF 897、IBLF 904与IBLF 914，以及深绿木霉（T. asperelloides）菌株IBLF 908用于该病害的生物防治。本研究在此基础上，评估了上述木霉菌菌株与巴西生菜种植中常用植保药剂的相容性。首先，在添加了供试药剂的培养基中测定菌株的菌丝生长情况；随后，将按商品推荐剂量搭载了植保药剂的拮抗菌诱饵与菌核施入培养盒（gerboxes），以此评估药剂对深绿木霉菌株IBLF 914寄生小核盘菌、核盘菌诱饵及菌核的能力，以及对生菜幼苗存活率的影响。试验结果显示：戊菌隆（pencycuron）、双炔酰菌胺（mandipropamid）与杀虫剂吡虫啉（imidacloprid）对木霉菌株的菌丝生长无显著影响；杀菌剂异菌脲（iprodione）对棘孢木霉菌株的菌丝生长无影响，但深绿木霉菌株对该药剂敏感，当药剂浓度达到10 µg·L⁻¹时即产生响应；腐霉利（procymidone）在药剂浓度达到10 µg·L⁻¹时即可抑制木霉菌株的菌丝生长；嘧菌酯（azoxystrobin）会降低拮抗菌的分生孢子萌发率，其半数致死剂量（LD50）范围为0.36~0.42 µg·L⁻¹。另一方面，在培养盒实验中，所有供试植保药剂均未降低拮抗菌对诱饵与菌核的寄生能力，也未削弱其对生菜幼苗上小核盘菌、核盘菌的防治效果。研究结果表明，使用棘孢木霉（Trichoderma asperellum）菌株IBLF 914开展生菜菌核病生物防治，可与巴西生菜种植中的其余植保措施兼容。